In the conveying arts it is well known to provide conveyor devices for continuous conveying of material, especially lump or granular materials such as coal, from one point to another. For example, in underground coal mining the mined coal typically must be transported from the mine face to a main haulage system remote from the face as mining proceeds. Among the various continuous conveyor systems proposed for this purpose have been those including an endless conveying element such as a flexible troughed belt trained for orbital travel about a closed loop path defining an upper conveying traverse overlying a lower inverted return traverse of the belt. Another conveyor system especially well adapted for transporting material in restricted spaces such as low coal mines comprises a flexible, endless conveying element including a deeply troughed conveyor belt which is driven in a generally horizontally extending closed loop path to define laterally side-by-side conveying and return traverses thereof extending longitudinally adjacent the laterally opposite sides of an elongated support frame assembly. The deeply troughed belt is thus maintained continuously upwardly open throughout a major part of both the conveying and return traverses thereof. The horizontal loop conveyor minimizes coal spillage and is well adapted for use in restricted head room inasmuch as its total vertical height corresponds to that of a single belt traverse rather than the two stacked or overlying traverses of conventional troughed belt conveyor systems. Such a horizontal loop conveyor system is disclosed in copending U.S. patent application Ser. No. 862,254, filed Dec. 19, 1977, the specification of which is incorporated herein by reference. The assignee in application Ser. No. 862,254 is the same as the assignee in the instant application.